Main Tube Research Articles

Phase separation and flow pattern modulation with a T-type micro-drainage system

T-junction is a classical structure for the two-phase separation. The analysis of gas-liquid flow and the interface movement at the T-junction is very important to the mechanism understanding especially for T-micro-junctions with unequal diameter joint. A simulation of the passive draining process and the corresponding flow pattern modulation of slug flow in a tube with three T-micro-junctions are presented in this paper. Using the volume of fluid (VOF) method and the dynamic grid adaption method the interface movement was tracked precisely especially at the region of drainage junctions. As results, with the separation of liquid no apparent change of gas slugs’ length but shortened water plugs. The gas fraction in main tube is increased more than 10%. During the separation process, the interface movement at unequal diameter junctions mainly consisted of three stages: the generation of penetrating bubbles, a stable sliding stage and the retraction to mother bubble. These constitute one piston movement of penetrating bubbles, which is the vital mechanism of phase separation. The cooperation of interface pressure difference, surface tension, interphase shear force and characteristic sizes of micro-channel drainages brings into a separation. A preliminary model to optimize characteristic sizes of porous materials is proposed in order to getting a successful liquid separation from a slug flow, which could improve the condensation heat transfer performance.

A new surgical technique of intra-scleral tube fixation in Ahmed Glaucoma Valve implantation: ‘Scleral Sleeve Method’

PurposeTo present a new surgical technique ‘Scleral Sleeve Method’ which would reduce the risk of Ahmed Glaucoma Valve (AGV) tube related complications in patients undergoing AGV FP7 (New World Medical Inc., Rancho Cucamonga, CA) for refractory glaucoma. DesignProspective, Non-Randomized, hospital based interventional case series. SubjectsA total of 16 eyes of adult patients (10 males and 6 females) with refractory glaucoma. MethodsInstead of using sutures to fix the AGV tube to sclera, we devised a novel method of intra-scleral tube fixation by creating a scleral tunnel fashioned in form of sleeve. Main outcome measurePost-operative tube related complications. ResultThere were no tube related complications such as exposure, extrusion or retraction in any of the cases. ConclusionUse of scleral sleeve method for tube fixation, along with graft to cover the tube, will provide additional safety measure and reduce the risks of tube related complications.

Intestinal epithelial organoids fuse to form self-organizing tubes in floating collagen gels.

Multiple recent examples highlight how stem cells can self-organize in vitro to establish organoids that closely resemble their in vivo counterparts. Single Lgr5+ mouse intestinal stem cells can be cultured under defined conditions forming ever-expanding epithelial organoids that retain cell polarization, cell type diversity and anatomical organization of the in vivo epithelium. Although exhibiting a remarkable level of self-organization, the so called 'mini-guts' have a closed cystic structure of microscopic size. Here, we describe a simple protocol to generate macroscopic intestinal tubes from small cystic organoids. Embedding proliferating organoids within a contracting floating collagen gel allows them to align and fuse to generate macroscopic hollow structures ('tubes') that are lined with a simple epithelium containing all major cell types (including functional stem cells) of the small intestine. Cells lining the central contiguous lumen closely resemble the epithelial cells on luminal villi in vivo, whereas buds that protrude from the main tube into the surrounding matrix closely resemble crypts. Thus, the remarkable self-organizing properties of Lgr5+ stem cells extend beyond the level of the microscopic cystic organoid to the next, macroscopic, level of tube formation.

Analysis of nozzle gas speed on the performance of the zoned and staged gas-fired radiant tube

In this study, the nozzle characteristics of zoned and staged double P-type gas-fired radiant tube were improved to optimize combustion efficiency. A three-dimensional finite element model was established, and a grid-independence study was conducted to guarantee the accuracy of the calculation results. Corresponding experiments were designed to prove the reliability and accuracy of the simulation model. Then, the developed mode was used to determine the flow field characteristics of the zoned and staged gas-fired radiant tube. Moreover, the gas and wall temperatures were calculated by altering the gas speeds in the main and branch tube nozzles respectively. The effects of nozzle gas speed on the radiant tube were compared. Results showed that increasing the air speed of the main tube nozzle could decrease the maximum temperature and the wall temperature difference, improve temperature uniformity, and slightly increase thermal efficiency. Increasing the air speed of the branch tube nozzle could reduce the maximum wall temperature and enhance surface temperature uniformity; but these effects were relatively not significant.

Design and Experimental Study of a Cascade Thermoacoustic Engine for Remote and Rural Communities

The design, construction, and experimental evaluation of a cascade thermoacoustic engine are presented in this paper. The system was designed and built under the constraint of an inexpensive device to meet the energy needs of the people based in remote and rural areas. From the cost and straightforward system point of view, the air at atmospheric pressure was applied as a working fluid, and the main resonator tubes were then constructed of conventional polyvinyl chloride (PVC) pipes. Such device consists of one standing-wave unit and one traveling-wave unit connected in series. This topology is preferred because the traveling-wave unit provides an efficient energy conversion, and a straight-line series configuration is easy to build and allows no Gedeon streaming. The system was designed to operate at a low frequency of about 57 Hz. The measured results were in a reasonably good agreement with the predicted results. So far, this system can deliver up to 61 W of acoustic power, which was about 17% of the Carnot efficiency. In the further step, the proposed device will be applied as the prime mover for driving the thermoacoustic refrigerator.

Implementation of a Decentralized PID Control System on an Experimental Platform Using LabVIEW

In this paper, the implementation of a decentralized control system is done on an experimental platform, which is dedicated to the study of fouling in industrial tubes. This plant is modelled as a multivariable system of order 2 × 2, whose the inputs are the voltage and current applied respectively in the plant actuators, and the outputs are flow and pressure measurements obtained by sensors in the main tube. The decentralized PID control system is performed by a supervisory system developed in LabVIEW software to verify the impact of fouling on the current behavior of the experimental platform, and thus enable performing predictive maintenance.

Failure analysis and erosion prediction of tee junction in fracturing operation

Erosion wear in piping is an unavoidable degradation process in the oil and gas industry that causes pipe wall thinning and leads to economic losses and potentially produce personal injuries. The mechanism of pipe erosion remains poorly understood. This study focused on predicting the erosion of a tee junction (T) under various flow types during fracturing operation. The failure analysis of tee junction was determined from its macroscopic features and scanning electron microscope (SEM) images and allowed definition of the failure mode and failure mechanism were defined, which appeared to be significantly different from what has been considered to be traditional. The failure analysis and fluid mechanics theory were used to build a computational fluid dynamics (CFD) simulation method to predict the erosion of the tee junction. The model of two-phase flow in a tee junction indicated that the solid-phase flow is determined by combined effects of the main tube flow, the flow inertia, and the turbulent flow. The distribution of the erosion in the tee was significantly different for various flow types and the simulation results were consistent with the results of the failure analysis. This model of predicted local distribution of erosion wear can assist the monitoring of pipe walls to prevent accidents and reduce maintenance labor.

Achieving an Ideal Position of the Tube in Anterior Chamber: A New Approach

Aim To describe a novel technique of tube placement in the anterior chamber. Methods In this technique, the extra cut piece of the tube is used to provide a hinge/fulcrum such that the main tube entering the anterior chamber would be angulated posteriorly away from the cornea. Results The tube entering the anterior chamber is angulated posteriorly. Conclusions Using a fulcrum beneath the tube would assist in posterior positioning of the tube and prevent long-term tube endothelial touch.

Experimental and 3D CFD analysis on optimization of geometrical parameters of parallel vortex tube cyclone separator

The air separators or vortex tubes are widely used in rotor craft engines. The air separators are used to provide an appropriate air stream (clean air) to helicopter engines. Vortex tubes are normally categorized according to direction of exiting flows. This article focuses on some results (both experimental and numerical) into the optimization and analysis of the separation performance/efficiency and fluid patterns in parallel vortex tubes (PVTs) as one of the most interesting types of air separators. Regarding the Ranque–Hilsch vortex tubes, the separated fluids (gas or liquid) or hot and cold streams (dirty and clean) leave the vortex tube at two different sides, in the case of parallel vortex tubes, both exhausts are located in one side (control valve position). In this research the effects of a new nozzle position (parallel injector), throttle orifice diameter (6.5–9.5 mm) and length of parallel main tube (180–220 mm) on the quality of the separation process in the Ranque–Hilsch and the parallel air separator (PVT) are analyzed. The results show that the parallel vortex tube with optimized length, injection angle and orifice diameter provides 66.08% (14.83 K) and 58.61% (13.88 K) higher thermal separation performance as compared to the initial parallel vortex tube.

Efficiency evaluation of vortex tube cyclone separator

The aim of the present investigation is analysis on separation phenomenon in a convergent cyclone separator affected by the structural factors including; throttle angle (15–45°), nondimensional throttle diameter (0.444–0.722), convergence main tube angle (2–12°), nondimensional convergent length (20–22.22), injector slots number (2–6) and injection pressure (4.5–6.5bar), as well as the numerical optimization of these parameters in terms of the separation efficiency using 3D-CFD methods (RSM). The initial experimental results show that, the separation improves with an increase in the nondimensional throttle diameter up to DRth=0.611, then beyond DRth=0.611, the separation capabilities are decreased. Also, the cyclone equipped with the throttle angle of α=30° provides 43.76% and 50.60% higher separation efficiencies as compared to the basic model. Furthermore, there are the initial optimum values (experiments) for the convergence angle and nondimensional length of main tube as β=10° and LN=21.66. Also, the separation efficiency improves with an increase in the slot number up to N=4. The comparison between the computed and laboratory outputs presents a favorable agreement with the maximum and minimum relative differences of 6.22% and 0.93%, respectively. In this study, the experiments determine the correct ranges for the factors, then, the exact optimum values will be selected by the CFD models.

Analysis of nozzle designs on zoned and staged double P-type gas-fired radiant tube

In this study, the nozzle characteristics of a zoned and staged double P-type gas-fired radiant tube were improved to optimize combustion efficiency. Experimental and numerical analyses were conducted on the optimized radiant tube. The deviation between the experimental and simulated monitoring parameters was less than 3.6%, thereby proving the reliability of the model. The gas and wall temperatures were compared by changing the positions of the main and branch tube nozzles, and structural parameters. The results showed that as the nozzle moved outward, the maximum surface temperature decreased from 1328K to 1320K, and the minimum wall temperature increased from 1253K to 1258K. When the branch tube nozzle was located at the intersection of the tee and branch tubes, the impact of high-temperature gas on the tube wall was reduced, and the uniformity of the branch radial temperature was improved. When the nozzle was fully premixed, the temperature difference was at its minimum. When the tube nozzle was asymmetric, the wall temperature difference was at its minimum, and combustion thermal efficiency was at its maximum.

Motion of a spherical capsule in branched tube flow with finite inertia

We computationally study the transient motion of an initially spherical capsule flowing through a right-angled tube bifurcation, composed of tubes having the same diameter. The capsule motion and deformation is simulated using a three-dimensional immersed-boundary lattice Boltzmann method. The capsule is modelled as a liquid droplet enclosed by a hyperelastic membrane following the Skalak’s law (Skalak et al., Biophys. J., vol. 13(3), 1973, pp. 245–264). The fluids inside and outside the capsule are assumed to have identical viscosity and density. We mainly focus on path selection of the capsule at the bifurcation as a function of the parameters of the problem: the flow split ratio, the background flow Reynolds number $Re$, the capsule-to-tube size ratio $a/R$ and the capillary number $Ca$, which compares the viscous fluid force acting on the capsule to the membrane elastic force. For fixed physical properties of the capsule and of the tube flow, the ratio $Ca/Re$ is constant. Two size ratios are considered: $a/R=0.2$ and 0.4. At low $Re$, the capsule favours the branch which receives most flow. Inertia significantly affects the background flow in the branched tube. As a consequence, at equal flow split, a capsule tends to flow straight into the main branch as $Re$ is increased. Under significant inertial effects, the capsule can flow into the downstream main tube even when it receives much less flow than the side branch. Increasing $Ca$ promotes cross-stream migration of the capsule towards the side branch. The results are summarized in a phase diagram, showing the critical flow split ratio for which the capsule flows into the side branch as a function of size ratio, $Re$ and $Ca/Re$. We also provide a simplified model of the path selection of a slightly deformed capsule and explore its limits of validity. We finally discuss the experimental feasibility of the flow system and its applicability to capsule sorting.

A porosity model for flow resistance calculation of heat exchanger with louvered fins

A full 3-dimensional flow simulation of a louvered fin heat exchanger assembly requires a huge number of grid points and enormous computing time. This work proposes a porous media model for the flow resistance calculation of the louvered fin side in order to efficiently simulate a complex 3-dimensional flow over the louvered fins. In the present model, we determine the permeability and Ergun constant in the modified Darcy equation. We first build up a database of the friction factor from the available experimental data and our own CFD data, and then develop the friction factor correlation in the range of the Reynolds number based on the louver pitch from 0.001 to 20000 for 14 different louvered fin types. We use the non-linear and multi-linear regression analyses to obtain the friction factor correlation as a function of louvered fin geometric parameters such as louver pitch, louver angle and fin pitch. The present friction factor correlation shows an excellent agreement with the previous experimental and CFD data. The modified Darcy equation with the proposed permeability and Ergun constant for the louvered fin side can easily be coupled with the 3-dimentional computation of the main tube flow.

Structural analysis of an elastomeric bellow seal in unsteady conditions: simulations and experiments

The present work describes a study carried out to characterize the constitutive and operating behavior of a rubber membrane, to be used as an air-oil separator in vibration dampers of helicopter rotor blades. The membrane is mounted inside the main damper tube through a manual reversal movement, has to withstand a differential pressure and elongation/shortening cycles without tearing, while complying with the dimensions allowed by the damper structure. FE analyses were used extensively, taking into account large displacements, as well as the hyperelastic, viscoelastic and pseudo-elastic characteristics of the rubber material. Material models were properly tuned relying on experimental evidence. The mechanical behavior of the membrane was simulated, starting from the very first loading cycles up to the assigned service life. Additionally, membrane samples and a damper mock-up were used to conduct several experimental tests, in the attempt to reproduce the mounting and operation phases of the component. A detailed comparison between experimental and numerical results, for validation purposes, yielded in all cases a good level of agreement.

Performance Evaluation of a Ranque-Hilsch Vortex Tube with Optimum Geometrical Dimensions

A brass Vortex Tube (VT) with interchangeable parts is used to determine the optimum cold end orifice diameter, main tube length and diameter. Experiments were carried out to study the effects of operating pressure as well. It is shown that there is an optimum value for cold end orifice diameter,which is equal to 4mm and there is an optimum value for cold and hot exit temperature difference at CF=0.4.A 2-D Computational Fluid Dynamics (CFD) model is validated against the present experimental data. CFD code is applied to investigate the role of vortex tube diameter and length on the temperature separation. The code is also used to investigate and analyze the highly rotating flow field structure and its characteristic with respect to various cold fractions. Finally the results are extrapolated for investigating the effect of inlet pressures up to 1053kPa, VT on separation performances.

Pedestrian Bridge Over Türr-channel Baja, Hungary: A Unique Arch Bridge Design

The Danube has a side branch in Baja, the Sugovica, from where the Türr-Channel opens. An innovative pedestrian bridge over the Türr-Channel in Baja, Hungary was opened for traffic in 2015. Bridging over the navigable channel faced serious difficulties due to the high flood level and significant ship traffic. The preliminary studies investigated movable and high positioned deck variations. The completed structure has 62 m span. The upper deck arch bridge is made of steel tube arches filled with concrete and rc. slab for the deck. Minimal structural height was necessary in the midspan to ensure the shipping clearance so the arch has the same plane as the deck in the midpoint. According to the high flood level and low clearance, the safety of the structure is ensured by filling concrete in the main girder tubes. The fabrication segments were assembled at site to 3 crane segments and were lifted to the temporary supports in the river. The concrete abutments became the part of the flood protection system. The unique shell-like cross girders and the slender arch gave a delightful bridge, which became the new symbol of the city. The bridge was built on sand with horizontally bended piles so the calculation had to examine the soil-structure iteration. The dynamic parameters were tested by dynamic load tests with the help of large group of people and with dropped truck.

A prospective, randomized comparative study for use of proseal laryngeal mask airway as an alternative to endotracheal intubation for airway management in children under general anesthesia

Introduction: Proseal laryngeal mask airway (PLMA) which is an upgraded modification of classic LMA, incorporating a gastric drainage tube lateral to the main airway tube which permits the regurgitated liquid gastric contents to bypass the glottis and prevents pulmonary aspiration. A prospective randomized interventional comparative study was performed to compare the efficiency of PLMA with a tracheal tube (TT) in pediatric patients with respect to number of attempts to placement of devices, hemodynamic responses and perioperative complications. Material and Methods: Sixty children, ASA physical status I and II weighing 10-20 kg between 2 and 8 years of age group of either sex undergoing elective infraumblical surgeries of 30-60 minutes duration, randomly divided into two group of 30 patients each. All patients were premedicated with IV midazolam and glycopyrrolate. General anesthesia with caudal epidural analgesia was given in all cases. IV propofal and sevoflurane was used for inducing general anesthesia. PLMA was inserted in group I and tracheal tube (TT) in patients of group II. In all cases after PLMA / TT insertion; caudal epidural analgesia was given and general anesthesia (GA) was maintained with O2, N2O and sevoflurane. Results: Ease of insertion was comparable in both the groups. There were no significant differences in mean oxygen saturation SpO2 (%) and end tidal carbon dioxide (ETCO2)) levels recorded at different time intervals between the two groups. However, highly significant changes in hemodynamic parameters were observed in the TT group. Complications such as nausea and vomiting (3.33%), sore throat (2%) and coughing (26.66%) were observed in the TT group. Conclusion: We concluded that PLMA could be used as an effective and safe airway device in children alternative to TT undergoing general anesthesia. Keywords: General anesthesia, Hemodynamic response, Paediatric, Proseal laryngeal mask airway, Tracheal tube

Effect of Tween-20 on Core Biomarkers Measured in Cerebrospinal Fluid from Patients with Alzheimer's Disease, Mild Cognitive Impairment, or Healthy Control Individuals.

There is substantial variation caused by preanalytical procedures in the measurement of cerebrospinal fluid (CSF) biomarkers for Alzheimer's disease (AD) reported in the literature. Determine whether the detergent Tween-20 improves diagnostic accuracy. CSF proteins (Aβ42, Aβ40, total tau, and phosphorylated tau) were measured by standard ELISA, in uncentrifuged CSF with or without 0.05% Tween-20 from patients with AD or amnestic mild cognitive impairment, and healthy elderly controls. In the main study, collection tubes containing Tween-20 (Sarstedt 15 mL) were filled with 5 mL CSF to ensure consistent detergent concentration across subsequent aliquots into Corning 2 mL tubes. These latter were also the primary collection vessel for samples without Tween-20. The effect of centrifugation, and extra tube transfer of samples with Tween-20 were also examined. 0.05% Tween-20 significantly increased mean measured CSF concentration of Aβ42 (30% ), Aβ40 (23% ), and total tau (4% ), but not phosphorylated tau. Generally, these increases were similar in all groups, although for Aβ42, the mean percentage increase with Tween-20 was slightly larger for AD. Areas under receiver-operator characteristic curves were similar whether Tween-20 was present or not. Centrifuged CSF without Tween-20 significantly reduced the measured concentration of Aβ42 versus non-centrifuged samples, a difference not seen when detergent was added. Similar CSF Aβ42 levels were found whether Tween-20 was added at collection in an extra tube or directly to the main collection tube. Addition of Tween-20 to CSF did not improve differentiation of patients from controls.

Application value of sleeve pancreaticojejunostomy in digestive tract reconstruction

Objective To investigate the application value of sleeve pancreaticojejunostomy in digestive tract reconstruction. Methods The clinical data of 40 patients who underwent sleeve pancreaticojejunostomy at the Affiliated Hospital of Luzhou Medical College between July 2013 and February 2015 were retrospectively analyzed. The head of pancreas and duodenal descending part were drifted out through Kouch technique, sections were sutured in braid-like U shape and the small pancreatic ducts were closed. The posterior wall of pancreatic stump and jejunal wall were sutured routinely and main pancreatic tube was implanted by silica gel with the thrum retained. The reserved lines were gone through at 6 o'clock and 12 o'clock in the jejunal wall to be sutured and knotted, making the jejunal mucosa set on the surface of main pancreatic duct like sleeve, and then the anterior wall pancreatic stump was sutured. The intraoperative situation and amylase concentration of drainage at post-operative day 1, 3, 5, 7 were observed and monitored. The patients were followed up for liver function, tumor markers, abdominal color Doppler ultrasound every 3 months and enhanced abdominal computer tomography every 6 months till May 2015. Measurement data with skewed distribution were presented as M(Qn) and analyzed by rank-sum test. Measurement data with normal distribution data were presented as ±s. Repeated measurement data were analyzed by the repeated measures ANOVA. Results All the 40 patients underwent sleeve pancreaticojejunostomy successfully. The duration of operation and pancreaticojejunostomy were (6.2±1.3) hours and (15±6) minutes, respectively. The volume of intraoperative blood loss was (370±55)mL and diameter of tumor was (2.5±1.5)cm. The amylase concentrations of drainage at postoperative day 1, 3, 5, 7 were 46.300 U (35.575 U, 68.600 U), 34.900 U (21.050 U, 55.550 U), 26.750 U (0.000 U, 41.400 U) and 0.000 U(0.000 U, 30.500 U), showing decrease trend with the time gone (F=97.268, P<0.05). Among the 40 patients, 2 had increase of drainage amylase concentration at anastomotic stoma with the drain amount less than 50 mL/d, showing normal temperature, no signs of abdominal pain and peritonitis and potential pancreatic leakage, they were recovered after symptomatic and supportive treatments. The other patients had no complications such as anastomotic leakage and hemorrhage. The duration of hospital stay of 40 patients was (18±5)days. Thirty-nine patients were followed up for 3-15 months, showing no postoperative anastomotic stenosis, acute or chronic pancreatitis and pancreatolithiasis, 1 of whom with recurrence tumor. Conclusion Sleeve pancreaticojejunostomy is easy to master, safe and reliable, and it is suitable for soft pancreatic tissue. Key words: Pancreatic diseases; Pancreaticoduodenectomy; Sleeve pancreaticojejunostomy

An open-structure sound insulator against low-frequency and wide-band acoustic waves

To block sound, i.e., the vibration of air, most insulators are based on sealed structures and prevent the flow of the air. In this research, an acoustic metamaterial adopting side structures, loops, and labyrinths, arranged along a main tube, is presented. By combining the accurately designed side structures, an extremely wide forbidden band with a low cut-off frequency of 80 Hz is produced, which demonstrates a powerful low-frequency and wide-band sound insulation ability. Moreover, by virtue of the bypass arrangement, the metamaterial is based on an open structure, and thus air flow is allowed while acoustic waves can be insulated.